Hi all, Given our message processing model, we do not enqueue message content in memory, and only keep message metadata. So, at the final point of a message delivery, we retrieve the message content accordingly and send.
However, if a user purges a queue while subscribers are receiving from it, all message content of that queue is deleted from the database, even though some messages might be at the final delivery stage. So when the message content of such a message is looked up, it will throw an NPE / NoSuchElementException. We cannot infer if the exception is due to a purge scenario or something else, because MessageContent can also be lost due to other reasons (e.g. : a message being acknowledged while it's second delivery attempt is on the way) I could think of following ways to handle this : 1. Catch the exception and add a general trace log explaining all possible reasons -> clear the message from in memory collections since we can safely say that its already been acked / purged. 2. Figure out and skip deleting the (message content + metadata) of enqueued / redelivered messages in-memory, and assume they will be deleted later from normal delivery flow. This means that all the in-memory, undelivered messages will still be delivered even after the queue is purged. (User can interpret this as an issue) Better suggestions ? The ideal solution would be to exactly remove all undelivered messages (in-store and in-memory) at the moment of purge. But this is difficult since the in-memory message buffer maybe delegated very fast into delivery jobs. As at now, I feel that "option 1" would be the most feasible solution. WDYT ? -- Cheers, Hasitha Amal De Silva Software Engineer Mobile : 0772037426 Blog : http://devnutshell.tumblr.com/ WSO2 Inc.: http://wso2.com ( lean.enterprise.middleware. )
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